Quick Answer
The Cummins NT855 and KTA19 cylinder heads most commonly fail from overheating (freeze cracking in cold climates, warpage in hot climates), head gasket blowthrough from improper installation, and valve seat wear after extended service. These are well-understood engines with abundant OEM parts availability worldwide.
- White smoke → head gasket or crack between coolant and combustion passages
- Engine overheating → head surface warpage disrupting head gasket seal
- Freeze cracking (cold climates) → coolant expansion cracking block walls and head
- Loss of compression → head gasket failure or crack in fire ring
- Oil in coolant → head gasket failure between oil and coolant passages
- Valve noise / tappet rattle → valve seat wear or collapsed lifter
Looking for a Cummins NT855 or KTA19 cylinder head? Get a free quote in 24 hours →
Why Trust This Guide
- 27+ years in diesel engine parts — Volgen Power has supplied Cummins parts to fleet operators in 70+ countries since 1998
- Factory-direct supply chain — NT855 and KTA19 cylinder heads sourced from verified Cummins industrial supply partners with full traceability
- 60,000+ crankshafts/year production capacity — backed by in-house manufacturing and quality control
- Real-world failure data — this guide is based on thousands of warranty claims and field reports from mining, marine, and power generation operators worldwide
Table of Contents
- Cummins NT855 / KTA19 Engine Overview
- 7 Common Cylinder Head Problems
- OEM Part Numbers Cross-Reference
- Torque Specifications
- Repair vs. Replace Decision Guide
- Buying Guide: 5 Steps
- Featured Parts
- FAQs
- Related Articles
Cummins NT855 / KTA19 Engine Overview
The Cummins NT855 is a 14-litre (855 cu in) inline-6 diesel engine producing 280–400 hp, used in industrial equipment, marine vessels, and power generation. The KTA19 is a 19-litre version producing 370–700 hp, used in large industrial equipment, marine propulsion, and stationary power. Both share the same basic cylinder head design philosophy: a robust cast iron head with individual port configuration for intake and exhaust.
[IMAGE: Cummins NT855 and KTA19 cylinder heads side-by-side comparison photo, with OEM part number locations circled/annotated]
| Specification | NT855 | KTA19 |
|---|---|---|
| Displacement | 14L / 855 cu in | 19L / 1150 cu in |
| Configuration | Inline-6, 2-valve/cylinder | Inline-6, 2-valve/cylinder |
| Bore × Stroke | 140 × 152 mm | 159 × 159 mm |
| Power Output | 280–400 hp | 370–700 hp |
| Head Part Numbers | 3411798, 3609849, 3411799 | 3088303, 3088304 |
| Head Gasket | 3890714 | 3890715 |
| Typical Application | Industrial, marine, generator | Mining, marine, heavy industrial |
7 Common NT855 / KTA19 Cylinder Head Problems
1. Freeze Cracking (Cold Climate Failure)
The NT855 and KTA19 are used in some of the world’s coldest operating environments — mining in Siberia, construction in Canada, and marine vessels in the Arctic. When coolant freezes inside the engine, the expanding ice creates enormous pressure that cracks the cylinder head, block, and freeze plugs. Freeze cracking is the most common catastrophic failure mode for these engines in cold climates.
Prevention: Always use proper coolant (not water) in cold weather. Install engine block heaters for overnight parking. Check the coolant freeze point at every service interval. Replace the thermostat on schedule — a failed thermostat can cause the engine to run cold, allowing coolant to freeze in extreme cold.
Real-world example: A mining operation in Yakutia, Russia lost three NT855 cylinder heads in a single winter when overnight temperatures hit −45°C and block heaters failed. After switching to a pre-heat protocol with redundant heaters and 60/40 antifreeze mix, they went two full winters without a single freeze crack.
[IMAGE: Freeze crack in cylinder head — example photo showing typical crack pattern from frozen coolant]
Need a replacement NT855 cylinder head with steel injector sleeves? Contact us for availability and pricing →
2. Overheating Warpage and Head Gasket Failure
In hot climates (the Middle East, Africa, Southeast Asia), the NT855 runs at high ambient temperatures. Restricted coolant flow from a clogged radiator, failed water pump, or low coolant level causes rapid overheating. The cylinder head is particularly vulnerable because it has the thinnest cross-section at the cylinder bridge areas.
A single overheating event above 110°C can permanently warp the head surface, making it impossible to maintain the head gasket seal on subsequent installations. Always check head flatness after any overheating event.
3. Head Gasket Blowthrough from Improper Installation
The NT855/KTA19 head gasket is a copper-asbestos or graphite composition design (older) or multi-layer steel (newer models). Improper installation is the leading cause of premature head gasket failure on these engines. Common errors:
- Not cleaning the block surface before head installation — debris prevents even clamping
- Using the wrong head gasket (different thickness for machined blocks)
- Not using new head bolts (old bolts may be stretched beyond specification)
- Incorrect torque sequence — must follow Cummins specified pattern
- Skipping the retorque procedure (NT855/KTA19 head bolts require retorque after initial heat cycles)
[IMAGE: Head gasket torque sequence diagram for NT855/KTA19]
Pro tip: The NT855 head gasket torque sequence is critical — always follow the star pattern and never skip the retorque step. See our torque specs table below for exact values.
4. Valve Seat Wear and Collapse
Valve seats in the NT855/KTA19 are inserted (pressed-in) components that can wear or, in extreme cases, collapse into the combustion chamber. Valve seat collapse is rare but catastrophic — it allows combustion gases to escape around the valve, destroying the engine. Valve seat wear causes loss of compression and power, especially noticeable at high loads.
Valve seat condition should be checked at every major overhaul. Replacement valve seats and valves are readily available for both engine families.
5. Injector Sleeve Failure (NT855)
The NT855 uses copper injector sleeves (in the cylinder head, around each injector). These sleeves can corrode from coolant contamination or galvanic action, causing coolant or oil to leak into the combustion chamber. This is a known design weakness of early NT855 engines. The fix is to replace the head with an updated design that uses steel injector sleeves — or to have the existing head rebuilt with steel sleeves at a machine shop.
If your NT855 has recurring coolant loss that is not from the head gasket, inspect the injector sleeves.
[IMAGE: Copper vs steel injector sleeve comparison — showing corrosion on copper sleeve]
Field case: A marine generator fleet in the Philippines was losing coolant every 200–300 hours on their NT855-powered gensets. Root cause: copper injector sleeve corrosion from seawater-cooled heads. After switching to steel-sleeve replacement heads from Volgen Power, coolant loss dropped to zero over 2,000+ operating hours.
Recurring coolant loss on your NT855? We stock steel-sleeve cylinder heads — get a quote →
6. Exhaust Manifold Cracking and Warpage
While not strictly a head problem, exhaust manifold cracking on the NT855/KTA19 can cause hot exhaust gases to leak onto the cylinder head, causing localized overheating and accelerating head gasket failure. The exhaust manifold on these engines runs very hot, and thermal fatigue cracks are common after 15,000–20,000 operating hours.
7. Main Bearing Web Cracking (KTA19)
The KTA19, running at higher power outputs and cylinder pressures than the NT855, is susceptible to main bearing web cracking under sustained high-load operation. This is a block failure mode, but it often causes the cylinder head to lose sealing as the block distorts under the stress. Main bearing web failure requires full block replacement and is a catastrophic failure — do not run the engine if rod knock or main bearing knock is suspected.
Cummins NT855 / KTA19 Cylinder Head OEM Part Numbers
| OEM Part Number | Application | Engine Family | Notes |
|---|---|---|---|
| 3411798 | NT855 | 855 cu in / 14L | Most common NT855 head, widely stocked globally |
| 3609849 | NT855 | 855 cu in / 14L | Alternate part, same application |
| 3411799 | NT855-P200 | 855 cu in / 14L | P200 performance variant |
| 3088303 | KTA19 | 1150 cu in / 19L | Most common KTA19 head |
| 3088304 | KTA19-M1 | 1150 cu in / 19L | Marine/industrial variant |
| 3411800 | KTA19-P600 | 1150 cu in / 19L | High-power industrial variant |
| 3890714 | NT855 Head Gasket | 14L | All NT855 applications |
| 3890715 | KTA19 Head Gasket | 19L | All KTA19 applications |
Not sure which part number fits your engine? Provide your engine serial number and we’ll confirm the correct head for your application.
NT855 / KTA19 Torque Specifications
| Fastener | NT855 Torque | KTA19 Torque | Notes |
|---|---|---|---|
| Head Bolts (Initial) | 165 Nm (120 ft-lbs) | 190 Nm (140 ft-lbs) | Follow Cummins torque sequence pattern |
| Head Bolts (Retorque) | 190 Nm (140 ft-lbs) | 210 Nm (155 ft-lbs) | After initial heat cycle, re-torque to final spec |
| Rocker Arm Bolts | 68 Nm (50 ft-lbs) | 68 Nm (50 ft-lbs) | Torque after head bolts are finalized |
| Injector Sleeve | 60 Nm (44 ft-lbs) | 60 Nm (44 ft-lbs) | Apply thread sealant before installation |
| Exhaust Manifold | 55 Nm (41 ft-lbs) | 55 Nm (41 ft-lbs) | Use anti-seize compound on threads |
[IMAGE: NT855/KTA19 head bolt torque sequence diagram — numbered star pattern]
Note: Always verify torque specifications against the Cummins service manual for your specific engine serial number. Values shown are typical — production variations may apply.
NT855 / KTA19 Repair vs. Replace Decision Guide
| Situation | Recommended Action | Est. Cost (USD) | Lead Time |
|---|---|---|---|
| Head gasket failed, head surface OK | Replace head gasket + resurface | $1,200–2,800 | 5–14 days |
| Freeze crack, single location, not in fire ring | Weld repair + stress-relief | $800–1,500 | 5–10 days |
| Multiple cracks or fire ring damage | OEM replacement | $2,500–4,500 | 7–21 days |
| Injector sleeve corrosion (NT855) | Replace with steel-sleeve head | $2,800–4,000 | 7–21 days |
| Valve seats worn but not cracked | Re-cut valve seats + new valves | $400–900 | 3–7 days |
| Head surface warpage | Replace if > 0.10mm | $2,500–4,500 | 7–21 days |
OEM vs. Aftermarket vs. Remanufactured: Which Should You Choose?
| Option | Pros | Cons | Best For |
|---|---|---|---|
| OEM New | Factory-spec fit, full warranty, guaranteed material quality | Highest upfront cost | Critical applications (marine, mining, power generation) |
| Aftermarket | Lower cost (30–50% less), widely available | Quality varies wildly, may not meet OEM metallurgy specs | Budget-conscious non-critical applications with trusted supplier |
| Remanufactured | 40–60% of new OEM cost, restored to spec | Depends on reman quality, shorter warranty | Cost-sensitive replacements where core is available |
Our recommendation: For NT855 and KTA19 engines in industrial, marine, or mining applications, always use OEM or verified-OEM-spec replacement heads. The cost difference is small relative to the downtime cost of a failed head in the field. A single cylinder head failure on a marine vessel or mining excavator can cost $10,000–50,000+ in lost production.
Cummins NT855 / KTA19 Buying Guide
1. Confirm the Engine Serial Number
Cummins engine serial numbers are critical for part identification. The serial number is stamped on the left side of the engine block above the oil pan rail. For the NT855, the serial number prefix identifies the engine series (e.g., 855-XXX indicates the displacement family). Always provide the serial number when requesting a quotation.
2. Identify the Cooling System Type
NT855 and KTA19 engines were produced with both seawater-cooled (raw water) and freshwater-cooled configurations for marine applications. The cylinder head design differs between these configurations — the seawater-cooled version has additional corrosion-resistant features. Make sure your supplier knows which configuration you have.
3. Check Head Weight for Shipping
NT855 cylinder head: approximately 68 kg bare. KTA19 cylinder head: approximately 95 kg bare. When quoted for international shipping, allow 85–100 kg for NT855 and 115–130 kg for KTA19. Sea freight from China is calculated on actual weight for these shipments. Request gross weight confirmation on the commercial invoice.
4. Verify Part Number Cross-Reference
The NT855 and KTA19 have multiple part number prefixes across their production history. The alternate part numbers (3609849 for NT855, 3088304 for KTA19) are fully interchangeable with the primary numbers in the same application. Verify with your engine serial number prefix.
5. Source from a Verified Industrial Supplier
Because these engines are used in critical industrial and marine applications, quality is paramount. A failed cylinder head on a generator set or marine vessel can strand equipment worth millions of dollars. Volgen Power has supplied Cummins cylinder heads to fleet operators across 70+ countries since 1998, with full traceability and warranty on every part. Learn about our quality process →
Featured Cummins NT855 / KTA19 Parts
Cummins NT855 Cylinder Head
OEM Part No: 3411798
14L / 855 cu in — Most common NT855 head
Steel injector sleeves available
Cummins KTA19 Cylinder Head
OEM Part No: 3088303
19L / 1150 cu in — Most common KTA19 head
For mining, marine & heavy industrial
NT855 Head Gasket
OEM Part No: 3890714
For all NT855 applications
Multi-layer steel (newer) or composite (older)
KTA19 Head Gasket
OEM Part No: 3890715
For all KTA19 applications
In stock, ships worldwide
Can’t find your part number? We carry the full range of Cummins NT855 and KTA19 cylinder heads, gaskets, and related components. Contact our parts team →
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Frequently Asked Questions
Are NT855 and KTA19 cylinder heads interchangeable?
No. The NT855 (14L) and KTA19 (19L) have different bore sizes, displacements, and cylinder head designs. They are not interchangeable. The NT855 head will not fit a KTA19 block, and vice versa. Always verify the engine model before ordering.
My NT855 has a copper injector sleeve problem. Can it be fixed without replacing the head?
Yes, but it requires a machine shop to: (1) remove the old copper sleeves, (2) install steel replacement sleeves, and (3) verify alignment and compression. This repair costs USD 600–1,200 at a competent machine shop. Alternatively, replace the head with one that already has steel sleeves installed — Volgen Power can supply this variant. Contact us for steel-sleeve NT855 heads →
How do I prevent freeze cracking on my NT855?
Use proper 50/50 antifreeze coolant (not plain water). Install and maintain engine block heaters. Never leave the engine standing with water in the cooling system during freezing weather. Check the coolant freeze protection level at the start of winter. Replace the thermostat if it has been in service for more than 3 years.
Can I rebuild my NT855 head instead of replacing it?
Yes, if the cracks are limited and the valve seats are serviceable. A typical NT855 head rebuild includes: valve seat grinding, new valve guides, new stem seals, and head resurfacing. Cost: USD 600–1,200. If the cracks are extensive or the fire ring is damaged, replacement is the only reliable option.
How long does it take to replace an NT855 cylinder head?
Labor time: 8–14 hours for a skilled technician. On marine engines with confined access (generator sets, marine propulsion), allow 14–20 hours. Resurfacing time if needed: 2–4 days at a machine shop. Total downtime: 5–21 days.
What is the Cummins NT855 cylinder head price?
OEM-spec NT855 cylinder heads (part number 3411798) typically range from $2,500–4,500 USD depending on condition (new vs. remanufactured), sleeve type (copper vs. steel), and shipping destination. Request a current quote with your engine serial number →
What is the KTA19 cylinder head replacement cost?
Total KTA19 cylinder head replacement cost (parts + labor) ranges from $4,000–8,000 USD in most markets. The head itself (part number 3088303) costs $3,500–5,500 USD. Labor varies by region and access difficulty. Marine applications are typically at the higher end due to confined workspace.
Related Articles
- Cylinder Head OEM Replacement Parts Guide — Complete cross-reference for Cummins, Volvo, Mercedes, and all major brands
- Diesel Cylinder Head Problems: 7 Common Issues — Failure mode overview and diagnosis guide
- Cylinder Head Repair: When to Fix vs Replace — Full decision matrix for head repair vs. replacement
- Cummins 6CT 8.3L Cylinder Head Guide — OEM part numbers and problems for the 6CT family
- Cummins 6BT 5.9L Cylinder Head Guide — OEM part numbers and problems for the 6BT family
- Volgen Power Cummins Parts Catalog — Full range of Cummins NT855, KTA19, ISX, and all Cummins engine parts
Last Updated: June 2026
Author: Volgen Power Technical Team
Originally Published: January 2026
